The gas mileage, power output, and emissions produced by an internal combustion engine depend in large part on the combustion efficiency of the engine, that is, the completeness of oxidation of a hydrocarbon fuel to carbon dioxide, water, and heat. Most internal combustion engines operate at far less than maximal efficiency and therefore achieve sub-maximal gas mileage, produce sub-optimal power, and emit high levels of emissions in the form of unburned fuel, carbon monoxide, and oxides of nitrogen. A well known strategy for increasing the efficiency and mileage of an internal combustion engine is to raise the temperature of the gas mixture present in the combustion chamber during the compression stroke of an engine cycle.
Several inventions have been disclosed to raise combustion chamber temperature through a heat transfer process, in which heat generated by combustion during the power stroke of an engine cycle is transferred directly or indirectly to the combustion chamber during the compression stroke. European Patent No. EP0717183 to Clarke discloses a moveable, permeable, disc-shaped regenerator which is situated within the cylinder of an internal combustion engine, between the piston and cylinder head. The regenerator oscillates on its own shaft, in a direction parallel to the movement of the cylinder. The regenerator absorbs heat from hot combustion gasses and transfers it to cool fresh air entering through an intake valve.
U.S. Pat. No. 6,340,004 to Patton discloses an engine in which the functions of an engine cycle are divided between two separate cylinders, including a compression cylinder for intake and compression, and a power cylinder, for power and exhaust. The two cylinders are connected by a passage including a thermal regenerator. Exhaust gasses from the power cylinder are used to heat the regenerator. Air from the compression cylinder is heated by the regenerator as it moves through the passage into the power cylinder.
These prior art devices require mechanically complex regenerators or heat exchangers, or specialized cylinders to carry out particular phases of an engine cycle. None of these devices can be integrated into, or retrofit onto, standard Otto cycle, Diesel cycle, or other internal combustion engines. There is a need for a simple heat transfer device that is readily integrated into existing production engine designs or retrofit onto an existing engine after production.